In the middle of the spinal column is the spinal canal that contains the spinal cord and other nerve roots. Herniated disks are a common source of lower back pain. Disks are cushions found between the vertebrae that make up the spinal column. The disks between the vertebrae allow the back to flex or bend. Disks also act as shock absorbers. The outer edge of the disk is a ring of cartilage called the annulus. The center of the disk is a gel-like substance called the nucleus. A disk herniates or ruptures when part of the center nucleus pushes the outer edge of the disk into the spinal canal, and puts pressure on the nerves.
As people age, the water content of the disk decreases, so it begins to shrink and the spaces between the vertebrae get narrower. Also, the disk itself becomes less flexible. Other conditions that can weaken the disk include:
- excessive weight which can squeeze the softer material of the nucleus out toward the spinal canal
- bad posture
- improper lifting
- sudden pressure (which might be slight)
The fibrous outer ring may tear. As the disk material pinches and puts pressure on the nerve roots, pain results. Sometimes fragments of the disk enter the spinal canal where they can damage the nerves that control bowel and urinary functions.
Low back pain affects four out of five people. So pain alone isn’t enough to recognize a herniated disk. However, if the back pain is the result of a fall or a blow to your back, don’t hesitate to contact a doctor. The most common symptom of a herniated disk is sciatica, a sharp, often shooting pain that extends from the buttocks down the back of one leg. This is caused by pressure on the spinal nerve. Other symptoms include:
- Weakness in one leg
- Tingling (a “pins-and-needles” sensation) or numbness in one leg
- Loss of bladder or bowel control (If you also have weakness in both legs, you could have a serious problem. Seek immediate attention.)
- A burning pain centered in the back
In disc herniations, the L5-S1 disc is involved 45% to 50% of the time, L4-5 40% to 45%, and L3-4 about 5%. Disc herniation at the other lumbar levels is rare. Sometimes the herniation is lateral, i.e., into the foramen. This is known as a far lateral disc herniation and occurs in about 3% to 10% of cases. Symptoms and signs vary, and it is common for different combinations of muscle and sensory loss to be present.
Diagnosing a herniated disk
Your medical history is key to a proper diagnosis. You may have a history of back pain with gradually increasing leg pain. Often a specific injury causes a disk to herniate. A physical examination can usually determine which nerve roots are affected (and how seriously). A simple x-ray may show evidence of disk or degenerative spine changes. MRI or CT scans or an EMG [nerve test] may be recommended if pain continues.
On the left image see the disk protruding below (disc #5), pushing the nerve sac to your right.
On the right image, you will see the dark gray disk material pushing the nerve sac down at the 5-1 level.
|Disc Level||Root Comp||Weakness||Reflex Involvement||Sensory Loss||Pain Distribution|
|L3 – L4||L4||Quadriceps, tibialis anterior||Knee jerk||Medial knee and shin||Anterior thigh|
|L4 – L5||L5||Extension of big toe||No significant||Big toe||Back of thigh, lateral calf|
|L5 – S1||S1||Gastrocnemius (ankle plantar flexion)||Achilles||Lateral foot and heel||Back of thigh and calf|
Non-surgical treatment usually works. Most back pain will resolve gradually with simple measures. Bed rest and over-the-counter pain relievers may be all that’s needed. Muscle relaxers, analgesic and anti-inflammatory medications are also helpful. You can also apply cold compresses or ice for no more than 20 minutes at a time, every hour or several times a day as necessary. After any spasms settle, you can switch to gentle heat applications.
Any physical activity should be slow and controlled so that symptoms do not return. Take short walks and avoid sitting for long periods. Exercises may also be helpful in strengthening back and abdominal muscles. Learning to stand, sit, and lift properly is essential to avoiding future episodes of pain.
- If non-surgical treatment fails, epidural injections of a cortisone-line drug may lessen nerve irritation and allow better participation in physical therapy. These shots are given on an outpatient basis over a period of weeks.
- Surgery may be required if a disk fragment lodges in spinal canal and presses on a nerve, causing a loss of function. The traditional surgical treatment is called a laminectomy and involves removing a portion of the vertebral bone. The surgery is performed under general anesthesia with an overnight hospital stay.
- Newer surgical techniques are microscopic and minimally invasive. Surgery is performed on an outpatient basis and you should be able to return to work in a few weeks.